Mechanical Clamping Devices (Fixtures) and its 7 Types

What are fixture clamping devices?
Fixture clamping devices are the mechanical clamps that hold the workpiece and keep it stable against all the distributing forces that come on it during a machining process.

Mechanical Clamping Devices (Fixtures)

The clamping devices should be clamped in such a way that the clamping pressure should not be directed towards the cutting operation (see above image).

The design of clamp should be such that it can be completely lifted from the workpiece while unloading it.

Well, there are more things about mechanical clamping devices that you should know.

Let’s dive right into it!

Types of Clamps in Jig and Fixture 

Different types of clamping and workholding devices used in jig and fixture are mentioned below;

  1. Screw clamp
  2. Hook bolt clamp
  3. Lever type clamps
    • Bridge clamp
    • Heel clamp
    • Swinging strap clamp
    • Hinged clamp
  4. Quick acting clamp
    • C-clamps
    • Quick acting nut
    • Cam operated clamp

Let’s discuss each of these fixture clamping devices one by one.

#1) Screw clamp

Screw clamp

Screw clamps are used to grip the workpiece from its edges so that the top surface of the workpiece can be machined easily.

Screw clamping method is simple but it consumes more time to clamp and unclamp the workpiece.

Also large effort is required to clamp the workpiece.

#2) Hook bolt clamp

Hook bolt clamp

A hook bolt clamp is a simple type of clamping device and it is used for light work only where other clamps are not applicable.

#3) Lever type clamps

A lever type clamp is a clamp that has a shape of a mechanical lever and holds the workpiece with the fixture that keeps it stable against all the distributing forces during a machining process.

There are 4 different types of lever type clamps used in jig and fixture.

  1. Bridge clamp
  2. Heel clamp
  3. Swinging strap clamp
  4. Hinged clamp

Bridge clamp

Bridge clamps are simple and reliable clamping devices in which the clamping force is applied by spring loaded nut.

The spring is also fitted with the clamp which allows its easy lifting when the nut is loosened.

The slot is provided in the clamp which allows its easy adjustment during the fitting.

Heel clamp

heel clamp

The heel clamps consist of a solid heel or a heel pin, a plate, strud, spring and a spherical washers.

The heel clamp is similar to that of bridge clamp, but it has a heel at the outer end of the clamp.

Above image is of a solid heel clamp which has a solid heel and a stop pin near the heel to prevent the rotation of the clamp during its fitting.

Swinging strap (latch) clamp

Swinging strap (latch) clamp

Swinging strap type clamps are the clamps which swings out or in.

You can see the two different designs for latch clamps in the above image.

Hinged clamp

hinged clamp

Hinged clamps are the type of clamps in which the latch is hinged to enable the workpiece loading and unloading.

#4) Quick acting clamp

Quick acting clamps are the type of mechanical clamping devices that can be operated quickly and saves a lot of labor time and operating time.

There are various types of quick acting clamps used in jig and fixture;

  1. C-clamps
  2. Quick acting nut
  3. Cam operated clamp


Quick acting clamp

There are basically two types of C-clamps;

  • Free C-clamp and
  • Captive C-clamp

In these clamps, the nut having a smaller size than the bore of workpiece is used.

The loading and unloading of the workpiece is done by rotating the C-clamp clockwise and anticlockwise.

Quick acting nut

Quick acting nut

Quick acting nut is a simple and effective fixture clamping device.

In quick acting nut, the threads are not continuous, but they are interrupted.

The nut has the length about 2-3 times the diameter of the threads.

The axis of hole is inclined about 3° to 7° to the axis of the nut.

Cam operated clamp

Cam operated clamp

Cam operated clamp is widely used in jig and fixture as it is very simple to operate (just by actuating the handle up and down).

This clamp is not convenient for those machining processes which produce more vibrations.

This is because the vibration shakes the clamp and reduces the clamping force.

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